Electronic oscillator tube



May 3, 1938. Y. ROCARD ELECTRONIC OSCILLATOR TUB E Filed Nov. 15, 1935 INVENTOR YVZROCARD v M ATTORNEY.

Patented May 3 19 UNITED STATES PATENT OFFICE ELECTRONIC OSCILLATOR TUBE Yves Rocard, Paris, France, assignor to Compagnie Generale de Telegraphic Sans Fil, a cor poration of France Application November 15, 1935 Serial No. 49,886

In France November 24, 1934,

4 Claims.

while for the particular case where the oscillator has its resonant circuit included in the plate circuit, means have beensuggested in order that ,5 there may be realized the following conditions:

there being taken into consideration in the calculations thenatural resistance inhering in the coils and (possibly) in the condenser. If these conditions are fulfilled, the angular frequency w is given by the equation A(w)=0 which has a solution independent of p and pa and this means a frequency stabilized in reference to the resistances of the grid and the plate.

The object of the present invention is to disclose ways and means adapted to insure stabilization which will hold good even if the tuned circult of the oscillator is not included in the plate 3Q circuit of the tube, to improve the stabilizing means indicated to be effective or efficient by elementary theory taking into consideration the harmonics introduced by the curvature (knee) of thecharacteristics of the tube, and augment and enhance the effectiveness of the said ways and means by the adoption of stabilizing means and maintaining a value constant 'at the limit of sustenance of oscillations or oscillatory state of the tube and this stabilizes the proportion of har- 40- monics generated and precludes frequency variations which might arise if the said proportion of harmonics were to vary.

In order that the nature of this invention may be better understood, it may be recalled here that the. arrangement of impedances Z, 21 in series with the plate and the grid of the oscillating tube, with a View to insuring stabilization of frequency, is known from the research of Fromy (LOnde Electrique, 1925) and of F. B. Llewellyn (Bell System Technical Journal, January, 1932, p. 6'7) and other investigators. However, what is dis regarded in these studies either partly (Fromy) or totally (by the other author) is the resistance residing in the impedances exterior to the tube,

' and this leads to solutions that are totally diflerent from the strictly accurate solution indicated in the present invention and which consists in giving the circuits the number of parameters, desired and to choose the same in such a fashion that there will be: I

there being duly included all of the resistance exterior to the tube.

The situation shall be illustrated by reference to an example shown in Fig, 1, which shows an oscillator of thekind previously considered by Fromy (only with the radio frequency circuits).

The solution suggested with a view to stabilization by the said author consists in regulating the capacities C1 and C2 in resonance with the inductances L1 and L2, respectively, to the pulsation Moreover, the coefficients of mutual induction M1 and M2 should be alike, in absolute values. Under these conditions (and this is fulfillable by means of individual setting or regulation of C1 and C2, and then'of M1 and M2) the angular frequency w is strictly equal to if the situation is kept very close to the oscillating limit, and this regardless of what may be r, n, 7'2, and p, pg.

It will be noted that, for this oscillator represented in Fig. 1, it is necessary to have three parameters in order to neutralize at one and the same-time 3(a)), C(w) and D(w), whereas in the oscillator disclosed in the above-mentioned copending patent application No. 11,905, two parameters are sufficient in order that the identical result may be obtained, whence it follows that the stabilization of the latter oscillator is easier, less expensive, and more convenient to regulate and insure. The oscillator comprising a tuned circuit disposed in the plate circuit, or, more generally and broadly speaking, in the circuit of an electrode which does not control the resistance of the oscillating grid, is by virtue of the said fact a preferred form of construction and embodiment of this invention.

Confining the following description to the case of an oscillator comprising a tuned circuit in the plate, novel ways and means for frequency stabilization shall be disclosed in which the harmonies are duly taken into consideration which will inevitably arise because of the curvature or knee in the characteristic of the tube.

If by way of calculation the state of oscillation of the triode presenting characteristics similar to the general curves, is ascertained, which is susceptible of giving a grid current i related to the grid voltage V by this condition i =j(V there results a system of simultaneous differential equations, hence those in which the characteristics of the tube play a part and which are nonlinear in nature. It will therefore be noted that the oscillation is not possible without the appearance of harmonics, and that these harmonics in the currents or the voltages act in two different ways upon the frequency, to wit: Because of lack of linearity of the characteristics, the frequency depending, in second approximation, upon the proportion of harmonics resulting from the adopted regulation, said proportion being itself a function of the characteristics of the tube and being thus in need of stabilization; generally these harmonics exercise a marked effect upon the phase of the voltages which reach the electrodes and being, to a certain extent, equivalent to a detuning of the stabilizing circuits, which results from the elementary study wherein p and pg have been treated as constants.

Now, according to this invention, the frequency is protected against fluctuations in the rate of the harmonics by maintaining the proportion thereof at a constant value by an action which comprises an amplification of these harmonics, detection and automatic regularization of the oscillation.

In the drawing, Fig. 1 is given to illustrate the principles of the invention, and shows a known circuit arrangement as modified by applicant by the inclusion of resistances, and Figs. 2

I to 5 illustrate different embodiments of the invention.

By way of example, Fig. 2 shows the ways and means comprising a multi-tube circuit arrangement adapted to the said end as applied to an oscillator of the kind dealt with in patent application No. 11,905, and in which the plate circuit of a four electrode oscillator tube is shunted by a parallel tuned circuit I forming a stopper in reference to the fundamental frequency, followed by two series circuits 2 in parallel with respect to each other, such that the combination of circuit I and circuits 2 wil1 be resonant to the frequencies of the chief harmonics (such as the second and third harmonics); at a point indicated by 3 in one of the circuits 2 there is taken off a potential which will be almost entirely due to the third harmonic, for-instance; amplification is effected in amplifier tube 1 and detection in a diode valve 5 in order to make available across a resistance 6 in the output of the diode a negative voltage corresponding to the amplitude of a typical overtone (say the third harmonic). This voltage is used for an anti-fading effect maintaining the oscillator in a stationary state, for instance, by an additional control grid I provided for this purpose in the oscillating tube 8.

It will be noticed that circuits I and 2 resulting in zero impedance in the plate circuit for the main harmonics exercise by themselves 'a stabilizing effect by preventing the harmonics of the plate circuit from circulating through the oscillating circuit and setting up harmonics in the grid voltage. However, since the existence of a grid current is itself generative of harmonics for the grid potential, it will be seen that this stabilizer effect is not sufficient.

One thus comes to the question of the means adapted to preserve the phase of the voltages arriving at the grid from the influence of the harmonics. For this purpose it is necessary to establish resonance of the grid circuit properly socalled not only for the fundamental wave, as

pointed out in the co-pending patent application above referred to, but also for all of the troublesome harmonics.

Fig. 3, by way of example, shows a single tube circuit arrangement adopted for this last pur-v pose. In scries with the coupling inductance L1 in the grid circuit of the oscillator tube 9, there are arranged as many parallel branches as there are undesirable harmonics to be eliminated, each of the said branches containing an inductance coil and a capacity in series L2 C2, L3 Ca, etc., save one branch finally which comprises only a capacity C1. All of these quantities are determined in a way so as to result in resonance of the assembly L1 C1 L2 C2 L3 C3, etc., with the fundamental and all of the harmonics of the current. If this is realized, conditions will be so that the control potential at the grid is simply given by the term di {"5 where i is the current in the inductance of the oscillation circuit just as if the oscillator were free from grid current.

If, for instance, it is deemed that only the second harmonic is undesirable, L3 C3 may be dispensed with, while making C1 of the value a L /f), C2 of the value sgjE-nc l 2J5 and L2 of the value In this way the impedance of the grid circuit for the fundamental and the second harmonic has been eliminated, and an oscillator is obtained whose stability is entirely satisfactory, even without the additional stabilization of frequency insured by maintaining the proportion of barmonies constant being really necessary.

It may be noted here that the oscillator shown in Fig. 3 offers already the property of reducing at the ration 1/11, the amplitude of the harmonic of nth order which would arise in the conventional type of oscillator where the inductance L in series with the oscillation circuit would be absent.

Fig. 4 shows an oscillator circuit which comprises'the combination of all of the stabilizing,

means disclosed in this invention, and more particularly illustrated in Figs. 2 and 3. In this figme, which shows amulti-tube circuit comprising an oscillator 8, an'amplifier 4- and a diode rectifier 5, the oscillator tube 8 is shown with a stabilizing grid 1 separated by a screen from the other electrodes. The oscillating plate may likewise be separated by means of a screen from the oscillating grid.

Fig. 5 shows another oscillation circuit comprising a combination of all the stabilizing means of the invention. This circuit is a combination of the features of Figs. 1, 2, and 3, and will be obvious from what has been set forth above in connection with the various figures.

After the descriptions hereinbefore given it may now be necessary to set forth What is disclosed in and claimed by the invention in a general way.

Assuming the characteristics of the tube to be linear, there is first insured stabilization according to the principles that have been indicated and consisting in making to strictly equal to regardless of what may be the plate and the grid resistances of the tube and the resistances of the outside circuits. This stabilization presupposes regulation at the oscillating limit and necessitates the provision of two supplementary impedances, one thereof in the grid circuit and the other one in the plate circuit, there being moreover one condition to be fulfilled as regards the couplings, though this condition is non-existent in a case where the oscillation circuit is connected in series with the circuit of an electrode which does not produce any appreciable control action upon the oscillating grid or grids.

Next the frequency is stabilized as regards the influence of the variations at the oscillating limit by the agency of automatic means of control of the proportion of the harmonics generated.

The stabilizing circuits finally are designed so that the potential at the control electrodes (grids) will not depend upon the harmonics, and that the harmonics of the current of the control electrodes will not get up electromotive forces in the oscillation circuit properly so-called.

Preferably the means here disclosed and claimed are used in combination, though it will be understood that the use individually or separately of some of these means may be susceptible of insuring results that will be quite satisfactory.

What I claim is:

1. In combination, an oscillation generator comprising a multi-electrode tube having a cathode, a grid electrode and an anode electrode, said grid electrode and anode electrode each connected to a circuit containing a definite ohmic resistance and coupling said anode and grid electrodes tothe cathode of said tube, an oscillating circuit containing an ohmic resistance and coupled at the same time with said grid and anode circuits without being inserted in series in any of said circuits, the coupling degree between said oscillating circuit and said grid and anode circuits being so adjusted that the tube is maintained at oscillation entertaining limit, and means for making the frequency generated independent of internal resistances of the tube and of ohmic resistances of the external circuits, the said means comprising a first predetermined impedance in the grid circuit a second predetermined impedance in the anode circuit,

there being a predetermined ratio of couplings between the oscillating circuit andthe said anode and grid. circuits respectively.

2. In combination, 'an oscillation generator comprising a multi-electrode tube having cathode, gridand anode electrodes, said grid electrode and anode electrode each connected to a circuit-containing a definite ohmic resistance and coupling said anode and grid electrodes to the cathode of said tube, an oscillating circuit containing an ohmic resistance and coupled at the same time with said grid and anode circuits, the coupling degree between said oscillating circuit and said grid and anode circuits being so adjusted that the tube is maintained at oscillation entertaining limit, a fundamental frequency and its harmonics being thus generated, means for making the fundamental frequency generated independent of internal resistances of the tube and of ohmic resistances of theexternal circuits, the said means comprising a first predetermined impedance in the grid circuit and a second predetermined impedance in the anode circuit, means connected tothe anode circuit for stopping the fundamental frequency and for passing predetermined harmonics, means for amplifying and deteoting one of the said harmonics, and means comprising a detected current controlled electrode in the tube for maintaining constant ratio between the amplitudes of the said harmonics and of the fundamental frequency.

3. In combination, an oscillation generator comprising a mu-lti-electrode tube having cathode, grid and anode electrodes, said grid electrode and anode electrode each connected to a circuit containing a definite ohmic resistance and coupling said anode and grid electrodes to the oathode of said tube, an oscillating circuit containing an ohmic resistance and coupled at the same time with said grid and anode circuits, the coupling degree between said oscillating circuit and said grid and anode circuits being so adjusted that the tube is maintained at oscillation entertaining limit, a fundamental frequency and its harmonics being thus generated, means for making the fundamental frequency generated independent of internal resistances of the tube and of ohmic resistances of the external circuits, the said means comprising a first predetermined impedance in the grid circuit and a second predetermined impedance in the anode circuit, the said first impedance comprising an inductance-capacity assembly so dimensioned that the grid circuit is resonant to the fundamental frequency and to the desired harmonics.

4. In combination, an oscillation generator comprising a multi-electrode tube having cathode, grid and anode electrodes, said grid electrode and anode electrode each connected to a circuit containing a definite ohmic resistance and coupling said anode and grid electrodes to the oathode of said tube, an oscillating circuit containing an ohmic resistance and coupled at the same time with said grid and anode circuits, the coupling degree between said oscillating circuit and said grid and anode circuits being so adjusted that the tube is maintained at oscillation entertaining limit, a fundamental frequency and its harmonics being thus generated, means for making the fundamental frequency generated independent of internal resistances of the tube and of ohmic resistances of external circuits, the said means comprising a first predetermined impedance in the grid circuit and a second predetermined impedance in the anode circuit, the said of the said-harmonics, and means comprising a detected current controlled electrode in the tube for maintaining constant ratio between the amplitudes of the said harmonics and of the fundamental frequency; r

, 5 .YVES ROCARD. 

